This invention relates to a print wheel of the daisy wheel type adapted for mounting in a printer, and more particularly to an integrally formed synthetic resin print wheel.
In prior print wheels, the support disc and the connected flexible character arms are commonly made of synthetic resin, metal, or a combination thereof. The central hub or cap portion of the print wheel is generally comprised at least in part of a rubbery resin or thermoplastic resin to frictionally grip the arbor spindle, while allowing facile removal for interchange of print wheels. Such a rubber hub or cap of this type is shown in the print wheel of U.S. Pat. No. 4,060,621 to Frechette and necessarily requires manufacturing operations directed to the separate molding of the rubber hub and the bonding of the hub to the support disc in addition to the molding of the disc and character arms.
Further, it is necessary in print wheels of this type that the diameter of the central passageway in the hub be held to close tolerances. To obtain a diameter within acceptable tolerances, it is generally necessary to machine the print wheel after the molding process, and this machining operation is not only costly but also may introduce problems related to shrinkage and deformation of the plastic from breaking the skin of the molded article. The myriad drawbacks of machining the molded piece and prior attempts to achieve acceptable diameter tolerance without machining are discussed in U.S. Pat. No. 4,264,222 to Bauer wherein a metal ring is disposed in the central passageway of the hub during the molding process to achieve controlled tolerances. However, this method requires an additional metal element, i.e., the metal ring, in addition to the plastic disc and the rubber hub.
It is an object of the present invention to provide a novel print wheel of the daisy wheel type that is integrally formed of synthetic resin.
It is also an object to provide such a print wheel having a hub providing a central passageway within desired diametrical tolerances as molded.
Another object is to provide such a print wheel wherein a multiplicity of spaced ribs are integrally formed in the central passageway of the hub to frictionally engage the spindle of an associated printer arbor assembly and permit facile interchange.
Yet another object is to provide such a print wheel that is economical to manufacture, durable and convenient in use, and refined in appearance.